Field of the Invention
The present invention relates to building construction methods, particularly to a method and unit that provides energy efficiency and structural soundness in buildings through a foam layer shell application.
Background Art
“Light framing” construction is a known construction mode using many small and generally closely spaced members that are assembled by nailing/screwing, and the mode includes balloon, platform and light-steel framing. Light framing building techniques are commonly used, especially in the USA, to erect residential, small commercial or light industrial structures. Light-frame construction using standardized dimensional lumber has become the prevailing light construction method in North America. Use of relatively minimal structural material allows builders to enclose a large area with minimal cost, while achieving a wide variety of architectural styles.
In light platform framing, each floor is framed separately, each floor level being framed as a separate unit or platform. Freed from the need to use heavy timbers (e.g., as with a post-and-beam system), platform framing offers ease of construction. Builders first fabricate a floor, which consists of wood joists and subflooring. The floor often serves as a working platform on which the stud wall frames are fabricated in sections and then lifted into place. A second floor, or the roof, is constructed atop the first-floor wall frame sections. The roof is formed of rafters (e.g., sloping joists) or wood trusses. The standard interior wall sheathing is gypsum board (drywall), which provides fire-resistance, stability, and a surface ready for interior finishing. Light framed structures traditionally have been constructed individually at each construction site; today many of the framing elements are mass-produced elsewhere and assembled on-site.
Modern light-frame structures typically obtain strength from rigid panels (plywood and/or other plywood-like composites such as oriented strand board (OSB) used to form all or part of wall sections). Until recent years, builders often employed any of several types of diagonal bracing techniques to stabilize framed walls. Diagonal bracing remains a vital interior part of many roof systems, and in-wall wind braces are required by building codes in many municipalities or by individual state laws in the USA. Special framed shear walls also are sometimes required to promote building structural strength, especially to foster compliance with earthquake engineering and wind engineering codes and standards.
Thus in commercial and residential construction, walls typically are framed up using vertical wooden or steel studs, to which an interior wall panel made of gypsum drywall (e.g., SHEETROCK® panel), fiberboard, traditional plaster, or the like is attached. Thereafter, exterior wall sheathing is used to enclose the wall and building and provide a surface for application of exterior finish materials, such as stucco, brick façade, shingles, aluminum or vinyl siding, etc. Insulating material, such as fiber glass, rock wool or cellulose, normally is sandwiched between the interior wall panel and exterior wall sheathing in order to thermally insulate the rooms and spaces of the building. Using this traditional method, there disadvantageously is little or no insulation present where the entire length of the vertical stud contacts the interior wall panel on one side, and exterior wall sheathing on the other side, providing a conduit for heat to readily escape the interior rooms, through the studs, to the outside environment.
The present invention solves this thermal insulation problem and also requires significantly less materials to achieve a highly energy efficient and structurally sound building. The presently disclosed method and system offers advantages of structural strength (potentially compliant with many building codes respecting wind and earthquake resistance) using fewer materials and less labor intensive methodology compared to fully conventional light framing construction. Less materials and ease of construction yields benefits of faster construction and reduced construction costs.
The present invention contemplates constructing a building using wall and ceiling panel assemblies that are made up of many traditional framing materials, but which are then coated with an insulating and strengthening foam. The foam layer initially is applied as viscous flowable foam, which may be sprayed in place. After controlled application, the foam layer then hardens into an enveloping shell which provides not only thermal insulation to the completed structure, but which also lends substantial structural strength. Moreover, because the foam shell substantially seals the interior of the structure against exterior weather, an exterior sheathing and an exterior façade are optional. A structure erected according to the present invention may be, if desired, substantially air tight and water tight (except where deliberately provided with doors, windows, vents, and the like). As the structure also is structurally sound and thermally insulated, the only reason to install an exterior sheath or additional roofing material is for aesthetic purposes.
While there are examples in the prior art of applied-foam insulating wall panels, none offer the advantages of the present invention.